In the bonding of integrated circuits, solder regions, copper pillars, or the like, are used for bonding device dies to package substrates. The dies and the package substrates, however, suffer from warpage. In addition, the packaging process often involves thermal processes, in which the packages are heated. Since the packages include different materials that have different Coefficients of Thermal Expansion (CTE), stresses are applied on the bonded packages. For example, the package substrates typically have greater CTEs than the device dies. This results in stresses to be applied to the solder regions. The stresses are also imparted to the device dies through the solder regions, causing dielectric delamination in the device dies.
One way of solving this problem is to use metal posts as the interconnection for the device dies and the package substrates. The metal posts are longer than typical solder regions and metal pillars, and hence may absorb the stress. The metal posts were formed by bonding a metal wire on one of the device dies and the package substrates, and then cutting the metal wire. The part of the metal wire left to connect to the bond ball is hence the metal post. This process, however, has a very low throughput. In addition, the uniformity in the lengths of the metal wires is difficult to control.